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The inclusion of low or non-fat dairy products which additional calcium in the diet may promote increased weight loss and improve insulin resistance. Therefore supplementing dairy products to obese subjects on a caloric restricted diet may be a useful strategy to enhance weight loss and improve insulin resistance. We therefore tested the short term effects of supplementing 56 overweight or obese (body mass index [BMI] >26 kg/m2) post menopausal women on a caloric restricted diet (1,400 kilocalories [kcal]) with two levels of dairy as yogurt on body composition, blood insulin, leptin and glucose concentration. The group consuming four supplemented dairy servings (DS-4) group were provided ~1400 mg Ca/day, and the group consuming two supplemented dairy servings (DS-2) were provided ~800 mg Ca/day.
Over the 3-months daily energy intake averaged 51% carbohydrate, 20.7% of protein and 27.6% of fat for both groups. At 3 months, the DS-4 group demonstrated decreased weight (87.7 to 86.2 kg, P=0.001), BMI (33.5 to 32.8 kg/m2, P < 0.001), total fat (36.1 to 34.7 kg, P<0.001), trunk fat (18.3 to 17.6 kg, P < 0.001). There were non-significant decreases in plasma glucose (74.7 to 71.1 mg/dl, P=0.494), leptin (32.5 to 31.3 µg/L, P=0.231) and insulin. For the DS-2 group there was decreased weight (86.4 to 84.4 kg, p<0.02), BMI (32.5 to 31.8 kg/m2, P=0.002), total fat (37.3 to 35.4 kg, P=0.003), trunk fat (17.1 to 16.5 kg, P = 0.27) and plasma leptin (27.8 to 25.2 µg/L, P=0.114). The DS-2 group demonstrated a surprising and significant increase in the fasting blood glucose with a marginal significant increase in insulin resistance as measured by HOMA at 3 months. We observed a significant treatment effect between the DS-2 and DS-4 groups for: % energy from fat (P=0.025), % energy from protein (P=0.047) and leptin (P=0.044).
Our study demonstrated the expected weight loss with caloric restriction but a paradoxical increase in blood glucose levels with dairy supplementation provided to maintain baseline calcium intake. Increasing dairy supplementation abrogated this small increase in fasting blood glucose and insulin resistance. The benefits of dairy calcium supplementation may be dependent on both the dose and the context of over all caloric intake.